1. Field of the Invention
The present invention relates to an information broadcasting system wherein a center office and a plurality of terminal equipment units are connected in a point-to-multipoint format through a network and the same information is broadcast from the center office to the plurality of terminal equipment units, more preferably to an information broadcasting system which sends the same information from a center office to a plurality of terminal equipment units in a broadband ISDN network.
In recent years, much research has been going on into broadband ISDN networks. It is projected that services will be offered which broadcast large volumes of data such as, for example, newspapers and others of the same media, to a large number of contractors through a public telecommunications network.
2. Description of the Related Art
One means of providing such a service is to provide one or more center offices, the origin of the broadcast, and broadcast from there to a plurality of contractors through a public telecommunications network.
When trying to establish such a service based on this idea, in the past it had been considered to broadcast information simultaneously to all the contractors. However an increase of the number of the contractors leads to increasing chances that not all contractors will be able to receive the broadcast without error. Therefore, even if a single contractor experiences error in reception, it is necessary to retransmit the information to all the contractors. Any attempt to retransmit information with the existing methods, however, requires the use of a retransmission protocol between the contractors and the center office, making it necessary for the center office to deal with all the contractors and thereby ending up increasing the processing load tremendously.
Instead of using a retransmission protocol with all the contractors, there is also the technique of repeatedly sending the same information a number of times to all the contractors, but this repeated transmission method means that the same information is sent several times even to contractors who have received the information normally, which is not only wasteful, but also poses therefor problem in that there is no certainty that the information will be received normally by all contractors even with multiple transmissions.